Most electronic devices, such as digital computers, include a power supply having a regulated output voltage. Typically, semiconductor based electronic devices operate at relatively low DC voltages such as five volts or less. However, much of the electrical energy to power electronic devices is made available at substantially larger voltages. For example, residential electrical power in the United States is nominally rated at 120 volts AC. Also, automotive power is nominally 12 volts DC, which is often subject to relatively high voltage transients during engine start and other changing load conditions.
Power supplies are generally employed to convert the available electrical power to a form usable by the electronic devices. A power supply used to power the electronic device typically includes a voltage regulator to maintain the output voltage within a range of values usable by the electronic device, e.g., five volts plus or minus two percent. If a voltage goes above the usable range of output values, it may damage the semiconductor device. Similarly, if the voltage goes below the range of output values, voltage compliance can be lost on one or more components of the electronic device, which may cause the device to stop operating. Also, changes in the output voltage of a power supply may induce noise into subsequent processing by other electronic devices and components.
A step-up regulator converts an input DC (Direct Current) voltage to another higher output DC voltage. The step-up regulator is useful in applications where a low source voltage is available and it is desired to maintain a stable output voltage higher than the source voltage. For example, the step-up regulators are useful in electronic circuit applications where multiple voltages are required to run different circuits and electrical components. Step-up voltage regulators are typically used in portable and desktop equipment, instrumentation, etc.
Most voltage regulators include at least one voltage reference. The voltage reference provides a reference voltage that is typically compared against the output of the voltage regulator. Feedback circuitry is employed to stabilize the output of the voltage regulator based on the reference voltage. Generally, some resistance is included in the feedback path for stabilization of the output voltage. However, such resistance may also create increased manufacturing costs and operational inefficiencies in the voltage regulator.